Tranexamic Acid in Trauma. ¿How Should We Use It [2013]

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Tranexamic acid in trauma: How should we use it? Lena M. Napolitano, MD, Mitchell J. Cohen, MD, Bryan A. Cotton, MD, MPH, Martin A. Schreiber, MD, and  Ernest E. Moore, MD,  Ann Arbor, Michigan T he CRASH-2 trial results have prompted trauma centers to conte mplat e wheth er tran exami c acid (TXA) shou ld  be added to their armamentarium for the treatme nt of bleed ing trauma patients. Primary brinolysis is integral in the patho- genesis of the acut e coag ulop athy of trau ma (ACOT) . 1  Y 5 Furt hermo re, some stud ies ha ve doc umented that the risk of death in trauma correlates signicantly with brinolysis. The presence of hyperbrinolysis (HF) in patients with severe trau mati c injuries is associat ed with a high mortali ty rate (70 Y 100%). 6  Y 9 The use of antibrinolytic agents in the treat- ment of the ACOT therefore has signicant biologic plausi-  bility . W e will revi ew the current knowledge of brinolysis in trauma and studies of antibrinolytic agents to make evidence-  based recommend ation s regard ing TXA use in trauma systems with mature hemostatic resuscitation protocols for the treat- ment of hemorrhagic shock patients. PATIENTS AND METHODS A comprehensive lite rature search was unde rtake n throug h PubMed and MEDLINE, using the follow ing keywords: tranexamic acid ,  antibrinolytic agents,  trauma,  injury ,  surgery ,   fibrinol ysis,  hemorrhage. Art ic les we re se lec te d if the to pi c was relevant to ‘‘tranexamic acid use in hemorrhage.’’ Addi- tional articles were identied by a careful review of reference lists. Ongoing clinical research studies for TXA and hemor- rhage were identied by search of  www.clinicaltrials.gov/ . Postinjury Fibrinolysis and Coagulation Coagulopathy, strictly dened as any perturbation of coagulation, occurs in nearly all patients after signicant in-  jury. 10 Impaired clotting after injury initially was thought to  be caused by iatro genic causes (hyp othermia, acidosis, hemo- dilution), which are sequelae of resuscitation. Impaired thrombin  production occurs secondary to hypothermia and acidosis. The deleterious effects of hemodilution and resulting factor de-  pletion include impaired protease cascade activation, impaired thro mbin prod ucti on, reduced plat elet function, and dys - functional brinogen bioavailability. 11,12 ACOT , initi ally desc ribed in 2003 , 13  Y 15 occurs in ap-  proximately 25% to 40% of patients nearly immediately when severe injury is combined with tissue hypoperfusion (shock), inde pend ent of iatro geni c causes. ACOT is assoc iated with increased blood prod uct requiremen ts, incre ased morbi dity , and mortality. 16,17 Additional studies suggest that ACOT occurs owing to of activation of the protein C system. 18 Protein C is a serine  protea se, which when acti vated (in a mechan ism that inv olves thrombin, endothelial protein C receptor, and thrombomodulin) results in a proteolytic deactivation of clotting factors Va and VIIIa and enhanced brinolysis by a mechanism mediated through a reduction in plasminogen activator inhibitor 1 (PAI-1, which normally inhibits t-PA), which in turn results in an in- crease in t-P A acti vity and incr ease d bri nol ysi s. 19 As a result , thrombin is bound, less clot is formed, and existing clot is more efciently lysed by existing brinolytic mechanisms. Blood coagulation has evolved into a highly tuned system capable of dynamic all y bala ncing eff ecti ve coag ulat ion to  prevent bleeding while preventing excessive thrombosis and brin depositio n. 20 Fibrino lys is is esse ntia l to this normal homeostasis and occurs primarily through the proteolytic ef- fect s of plasmin. Plas min is forme d by the clea vag e of its inacti ve zymogen (plasminoge n) by either tissue plasminogen activator (t-P A) or by urokinase (UPA). t-P A and UPA are both effectively cleaved by plasmin, resulting in increased activity. Fibrin also works in a positive feedback role: in the presence of brin, t-PA and UPA possess increased afnity and activity on plasminogen.  Negative control of the brinolytic system comes from direct inhibition of plasmin by P AI-1 and thrombin activatable brinolysis inhibitor (TAFI), which block the conversion of  plasmi noge n to plasmin, thus inh ibitin g brinol ysis. > 2 -plasmin inhibi tor d irectl y inh ibits plasmi n. Plasmin is protec ted from > 2 -  pla smin inhi bito r whil e bou nd to br in. Thromb in activ atable -  brin ol ysis inhib ito r serv es to bre ak this bond , ren deri ng pla smin susceptible to inhibition. While the mechanisms of trauma- induced brinolysis remain speculative, the activated protein C sys tem is impl icat ed. Acti vat ed pro tei n C (APC) dir ect ly inh ibi ts PAI-1, thereby limiting the negative control of t-PA, allowing  plasmi n inhibi tion. How to Determine Postinjury Fibrinolysis: Role of Thromboelastography and Thromboelastometry Identication of pos tinj ury bri nol ysis can be chal- lenging. The traditional laboratory test for pathologic bri- nolys is has been the euglobulin lysis time (EL T). In brief, the euglobulin fraction (pre pare d by acid ica tion) of citr ated , R EVIEW ARTICLE  J Trauma A cute Care Surg Volume 74, Number 6  1575 Submitted: January 25, 2013, Revised: March 13, 2013, Accepted: March 17, 2013. From the Division of Acute Care Surgery (L.M.N.), Department of Surgery, Uni- versi ty of Michi gan, Ann Arbo r, Michigan; Divisi on of Gener al Surge ry (M.J .C.), San Franc isco General Hospi tal, University of Calif ornia, San Francisco, California; Division of Acute Care Surgery (B.A.C.), Department of Surge ry , Uni versi ty of T exas Medic al School at Houst on, Houst on, Texas; Section of Trauma and Critical Care (M.A.S.), Department of Surgery, Oregon Health & Science University, Portland, Oregon; and Division of Acute Care Surge ry (E.E. M.), Depart ment of Surge ry , Denv er Healt h Medica l Center , Denver, Colorado. Address for reprints: Lena M. Napolitano, MD, Acute Care Surgery, [Trauma, Burns, Crit ical Care , Emer genc y Sur gery ], Depa rtment of Sur gery , Uni vers ity of Michigan Health System, Room 1C340-UH, Univ ersity Hospital, 1500 East Medical Dr, SPC 5033, Ann Arbor, MI 48109-5033; email:  [email protected]. DOI: 10.1097/T A.0b013e318292cc54 Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

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uno del ácido tranexamico en trauma

Transcript of Tranexamic Acid in Trauma. ¿How Should We Use It [2013]

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Tranexamic acid in trauma: How should we use it?

Lena M. Napolitano, MD, Mitchell J. Cohen, MD, Bryan A. Cotton, MD, MPH, Martin A. Schreiber, MD,

and  Ernest E. Moore, MD,  Ann Arbor, Michigan

The CRASH-2 trial results have prompted trauma centersto contemplate whether tranexamic acid (TXA) should 

 be added to their armamentarium for the treatment of bleedingtrauma patients. Primary fibrinolysis is integral in the patho-genesis of the acute coagulopathy of trauma (ACOT).1 Y 5

Furthermore, some studies have documented that the risk of death in trauma correlates significantly with fibrinolysis.The presence of hyperfibrinolysis (HF) in patients with severetraumatic injuries is associated with a high mortality rate(70 Y 100%).6 Y 9 The use of antifibrinolytic agents in the treat-ment of the ACOT therefore has significant biologic plausi- bility. We will review the current knowledge of fibrinolysis intrauma and studies of antifibrinolytic agents to make evidence- based recommendations regarding TXA use in trauma systemswith mature hemostatic resuscitation protocols for the treat-ment of hemorrhagic shock patients.

PATIENTS AND METHODS

A comprehensive literature search was undertakenthrough PubMed and MEDLINE, using the following keywords:tranexamic acid ,  antifibrinolytic agents, trauma,  injury, surgery,

  fibrinolysis,   hemorrhage. Articles were selected if the topicwas relevant to ‘‘tranexamic acid use in hemorrhage.’’ Addi-

tional articles were identified by a careful review of referencelists. Ongoing clinical research studies for TXA and hemor-rhage were identified by search of  www.clinicaltrials.gov/ .

Postinjury Fibrinolysis and CoagulationCoagulopathy, strictly defined as any perturbation of 

coagulation, occurs in nearly all patients after significant in- jury.10 Impaired clotting after injury initially was thought to be caused by iatrogenic causes (hypothermia, acidosis, hemo-dilution), which are sequelae of resuscitation. Impaired thrombin production occurs secondary to hypothermia and acidosis. Thedeleterious effects of hemodilution and resulting factor de- pletion include impaired protease cascade activation, impaired 

thrombin production, reduced platelet function, and dys-functional fibrinogen bioavailability.11,12

ACOT, initially described in 2003,13 Y 15 occurs in ap- proximately 25% to 40% of patients nearly immediately whensevere injury is combined with tissue hypoperfusion (shock),independent of iatrogenic causes. ACOT is associated withincreased blood product requirements, increased morbidity,and mortality.16,17

Additional studies suggest that ACOT occurs owing toof activation of the protein C system.18 Protein C is a serine protease, which when activated (in a mechanism that involvesthrombin, endothelial protein C receptor, and thrombomodulin)results in a proteolytic deactivation of clotting factors Va and VIIIa and enhanced fibrinolysis by a mechanism mediated through a reduction in plasminogen activator inhibitor 1 (PAI-1,which normally inhibits t-PA), which in turn results in an in-crease in t-PA activity and increased fibrinolysis.19 As a result,thrombin is bound, less clot is formed, and existing clot ismore efficiently lysed by existing fibrinolytic mechanisms.Blood coagulation has evolved into a highly tuned systemcapable of dynamically balancing effective coagulation to prevent bleeding while preventing excessive thrombosis and fibrin deposition.20 Fibrinolysis is essential to this normalhomeostasis and occurs primarily through the proteolytic ef-

fects of plasmin. Plasmin is formed by the cleavage of itsinactive zymogen (plasminogen) by either tissue plasminogenactivator (t-PA) or by urokinase (UPA). t-PA and UPA are botheffectively cleaved by plasmin, resulting in increased activity.Fibrin also works in a positive feedback role: in the presenceof fibrin, t-PA and UPA possess increased affinity and activityon plasminogen.

 Negative control of the fibrinolytic system comes fromdirect inhibition of plasmin by PAI-1 and thrombin activatablefibrinolysis inhibitor (TAFI), which block the conversion of  plasminogen to plasmin, thus inhibiting fibrinolysis.>2-plasmininhibitor directly inhibits plasmin. Plasmin is protected from>2- plasmin inhibitor while bound to fibrin. Thrombin activatable fi-

 brinolysis inhibitor serves to break this bond, rendering plasminsusceptible to inhibition. While the mechanisms of trauma-induced fibrinolysis remain speculative, the activated protein Csystem is implicated. Activated protein C (APC) directly inhibitsPAI-1, thereby limiting the negative control of t-PA, allowing plasmin inhibition.

How to Determine Postinjury Fibrinolysis: Role of Thromboelastography and Thromboelastometry 

Identification of postinjury fibrinolysis can be chal-lenging. The traditional laboratory test for pathologic fibri-nolysis has been the euglobulin lysis time (ELT). In brief, theeuglobulin fraction (prepared by acidification) of citrated,

R EVIEW ARTICLE

 J Trauma Acute Care Surg Volume 74, Number 6    1575

Submitted: January 25, 2013, Revised: March 13, 2013, Accepted: March 17, 2013.From the Division of Acute Care Surgery (L.M.N.), Department of Surgery, Uni-

versity of Michigan, Ann Arbor, Michigan; Division of General Surgery(M.J.C.), San Francisco General Hospital, University of California, SanFrancisco, California; Division of Acute Care Surgery (B.A.C.), Department of Surgery, University of Texas Medical School at Houston, Houston, Texas;Section of Trauma and Critical Care (M.A.S.), Department of Surgery, OregonHealth & Science University, Portland, Oregon; and Division of Acute CareSurgery (E.E.M.), Department of Surgery, Denver Health Medical Center,Denver, Colorado.

Address for reprints: Lena M. Napolitano, MD, Acute Care Surgery, [Trauma, Burns,Critical Care, Emergency Surgery], Department of Surgery, University of Michigan Health System, Room 1C340-UH, University Hospital, 1500 East Medical Dr, SPC 5033, Ann Arbor, MI 48109-5033; email:  [email protected].

DOI: 10.1097/TA.0b013e318292cc54

Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

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 platelet-poor, diluted plasma is allowed to clot. The ELT is thetime for spontaneous lysis of the clot (normal range, 60 Y 300minutes). Unfortunately, the obligatory laboratory time to prepare the ELT exceeds 4 hours. Moreover, the ELT doesnot assess fibrinolysis in whole blood. In contrast, thrombo-elastography (TEG) (Haemonetics, Braintree, MA) and thrombo-

elastometry (ROTEM) (Tem International, Munich Germany) provide a rapid assessment of fibrinolysis in whole blood.21 Y 24

In the TEG system, fibrinolysis is typically recorded as the percent lysis at 30 minutes (LY30) after reaching themaximum amplitude. The% lysis represents the reduction of the area under the curve. The range in healthy adults is re- ported to be 0% to 7.5%, although in the Denver experience, it has always been less than 3% in normal individuals.25 Esti-mated percent lysis (EPL) is available 2 minutes after maxi-mum amplitude and recalculated every 30 seconds thereafter to project the ultimate LY30. In general, EPL underestimatesLY30. A small early increase in LY30 unrelated to fibrinolysismay occur owing to clot retraction from hyperactive platelets.26

A new TXA-inhibitable assay has been developed to obviatethis artifact.In the ROTEM system, fibrinolysis is usually reported 

as LI30 (Lysis Index after 30 minutes), which, in contrast toLY30, is the percentage of maximum clot firmness (amplitude)remaining 30 minutes after the initiation of clotting. Thenormal LI is 94% to 100%. The previously reported ROTEM parameter maximum lysis is the percent reduction of maxi-mum clot firmness at 60 minutes. Thus, it is difficult to in-terpret studies of fibrinolysis in comparing TEG versusROTEM. Interestingly, the TEG functional fibrinogen assayand the ROTEM FIBTEM are more sensitive in detecting fi- brinolysis than LY30 or LI30.22

Although TEG and ROTEM provide more rapid datafor fibrinolysis compared with previous techniques, there aresignificant limitations with these techniques since the ACOTis a dynamic process and frequent changes may occur.27 Bothtests can be performed as point of care, and the faster avail-ability of results may assist clinical decisions of TXA use aswell as what, when, and how much blood products to trans-fuse.28 Preliminary test results are obtained as early as 5 minutes,with full results available within 20 minutes after starting theanalysis.29 We believe that viscoelastic studies should have a rolein the clinical care of patients with ACOT and ongoinghemorrhage.

We also recognize that there may be occult HF in traumathat is not diagnosed by viscoelastic studies. In a prospective

study of 303 trauma patients, thromboelastometry (TEM) HFwas defined as maximum clot lysis of greater than 15%, and fibrinolytic activation was determined according to plasmin-antiplasmin (PAP) complex and   D-dimer levels.30 Only 5% of  patients had severe fibrinolysis on TEM, but 57% of patients had evidence of ‘‘moderate’’ fibrinolysis, with PAP complex levelselevated to more than twice normal without lysis on TEM. At  present, we do not know what is pathologic ‘‘hyperfibrinolysis.’’PAP complexes and   D-dimer levels signify that clotting (fibrincross-linking) has occurred, and the innate response to controlclot progression is plasmin degradation.31 Whether this HF isclinically significant and warrants treatment has yet to be deter-mined. The criterion standard for measurement of HF remains

ELT. As stated previously, the TEG functional fibrinogen assayand the ROTEM FIBTEM may be more sensitive in detectingfibrinolysis compared with maximum clot lysis by TEM. Ad-ditional research is required in this important area, and in par-ticular, development of a standardized measurement of HFin trauma is needed.

HF in Trauma: How Common?The incidence of HF ranges from 2% to 34% and seems

to vary based on the instrument measuring fibrinolysis, howsoon after injury the sample is drawn, the threshold selected,and the severity of injury. The Denver study of 61 trauma patients requiring transfusion during the resuscitative phasereported that HF (defined as EPL  9  15% by r-TEG) occurred in 11 patients (18%). However, this finding was present in34% of those patients requiring massive transfusion (MT)compared with only 2% of the remainder. HF was associated with significantly increased mortality, and with a depressed fibrinogen and prolonged partial thromboplastin time values.1

A single-center study of 1996 highest-level trauma ac-tivations admitted directly from the scene demonstrated that HF (defined as   97.5% LY30 by r-TEG) was present in only41 patients (2%) on arrival.32 More importantly, this groupfound that mortality doubled when the admission LY30 ismore than 3%, which occurred in 7% of the severely injured.Based on these data, the Memorial Hermann Hospital clinicalguideline recommends TXA infusion only in bleeding trauma patients if r-TEG confirms LY30 of more than 3%.33 The Denver group now uses the same threshold of LY30 of more than 3%for TXA administration because of a similar observation.25

Investigators from LA County identified HF (defined asEPL  9  15%) in 10% of their patients (n = 118) through serialTEG on admission and 1, 2, and 6 hours. Of note, 62% of theHF patients died of hemorrhage by 6 hours. Of those whosurvived 6 hours, 92% eventually died of either hemorrhageor head injury. HF was a strong independent predictor of need for MT and mortality.34

Looking at a more critically injured cohort, the SanFrancisco group noted that 20% of 115 patients had HF, de-fined as an admission maximal clot lysis of 10% or higher. Aswith other studies, this group found that HF was associated with multiorgan failure (63.2% vs. 24.6%,  p  = 0.004) and mor-tality (52.2% vs. 12.9%,  p  G  0.001).17 In evaluating the pub-lished work on this lethal presentation, several key risk factorsfor HF have been identified (Table 1).

The LA County and Houston groups noted that in-

creasing Injury Severity Score (ISS) was associated with sig-nificantly increasing likelihood of presenting with HF, contraryto studies from Denver and San Francisco. Shock on arrivaland admission hypothermia were strong predictors of HF at all 4 centers. Base deficit was confirmed as an independent  predictor of HF by Ives et al.34, Cotton et al.32, and Kashuk et al.1, but not by Kutcher et al.17

Tranexamic AcidTXA, a synthetic derivative of the amino acid lysine, is

an antifibrinolytic agent that acts by binding to plasminogen and  blocking the interaction of plasminogen with fibrin, thereby pre-venting dissolution of the fibrin clot.35 TXA has been available

 J Trauma Acute Care Surg Volume 74, Number 6  Napolitano et al.

1576   *   2013 Lippincott Williams & Wilkins

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for more than 20 years. It was first approved by the US Food and Drug Administration (FDA) in 1986 for short-term use(2 Y 8 days) as an injection to reduce or prevent bleeding duringtooth extraction in hemophilia patients.36 In November 2009,the FDA approved the oral form of TXA to treat menorrha-gia.37,38 All other uses of TXA, including trauma use,are considered ‘‘off-label’’ uses.

CRASH-2 TrialThe CRASH-2 Trial was a large pragmatic international

randomized placebo-controlled trial of the effects of the earlyadministration of TXA (1 g over 10 minutes intravenously ad-ministered, then intravenous infusion of 1 g over 8 hours) on28-day hospital mortality, vascular events, and transfusionsin adult trauma patients.39 The trial enrolled 20,211 patientswith, or at risk of, significant bleeding from 274 hospitalsacross 40 countries, with no significant difference in baselinecharacteristics. The inclusion criteria were as follows:

&   Adult trauma patients with significant hemorrhage&   Systolic blood pressure (SBP) less than 90 mm Hg, heart 

rate of more than  9 110 beats per minute, or both&   Within 8 hours of injury

The fundamental eligibility criterion was whether theresponsible doctor was ‘‘substantially uncertain’’ as to whether to use an antifibrinolytic in the trauma patient.40 The authorshave disclosed that 20,225 patients were screened, and 20,211 patients were randomized, leaving only 14 patients who wereexcluded.41

All-cause 28-day mortality was 1,463 (14.5%) in TXAand 1,613 (16.0%) in placebo patients (relative risk [RR], 0.91;95% confidence interval [CI], 0.85 Y 0.97;   p  = 0.0035). All-cause mortality reduction was 1.5%, giving a number needed to treat (NNT) of 67 to save one life over 28 days. Considering

the mortality benefit and the absence of evidence in the studyto suggest a risk of harm, this is a significant result. On the basis of the CRASH-2 Trial results, i t has been estimated that TXA use could save between 70,000 and 100,000 lives per year worldwide.42

Since TXA is an antifibrinolytic agent whose primarymechanism of action is reduction in clot lysis, the potential for 

increased thromboembolic events was evaluated. Secondaryoutcomes were vascular occlusive events (myocardial infarction,stroke, pulmonary embolism [PE] and deep vein thrombosis[DVT], surgical intervention [neurosurgery as well as thoracic,abdominal, and pelvic surgery]), receipt of blood transfusion,and units of blood products transfused. There was no differ-ence in the rate of vascular occlusive events between groups:no difference in venous thrombotic events (PE 72 [0.7%] for the TXA group vs. 71 [0.7%] for the control group; DVT 40[0.4%] for the TXA group vs. 41 [0.4%] for the control group)or risk of stroke (57 [0.6%] for the TXA group vs. 66 [0.5%]for the control group). There was a reduced risk of myocardialinfarction in the TXA group (35 [0.3%] for the TXA group vs.

55 [0.55%] for the control group).

Closer Look at Mortality in CRASH-2 TrialOnly approximately 5% of patients had bleeding as a

cause of death, and these were early deaths, with most oc-curring within the first 48 hours after injury. Mortality caused  by bleeding was 489 (4.9%) in the TXA group and 574 (5.7%)in the control group (RR, 0.85; 95% CI, 0.76 Y 0.96;   p   =0.0077). There were no significant differences in mortalitydue to any other cause (cause of death was defined by thefollowing categories: bleeding, vascular occlusion [myocar-dial infarction, stroke, and PE], multiorgan failure, head in- jury, and other). Traumatic brain injury (TBI) was the leading

TABLE 1.   Mortality and Risk Factors Associated With Development of HF

No. Patients Prevalence of HFDiagnostic Measure and

C riteria for H F Mortality Rate for H F R isk Factors for H F

Cotton et al.32 1,996 2% LY30  9  7.5% by admission r-TEG 76% Increasing base deficit  

SBP  G  90 mm Hg

Increasing ISS

Prehospital fluids

Ives et al.34 118 11% EPL  9  15% by serial TEG 92% Increasing lactate

Increasing base deficit SBP  G  90 mm Hg

ISS  9  16

Kashuk et al.1 61 18% EPL  9  15% by serial r-TEG 64% Increasing base deficit  

Increasing lactate

SBP  G  90 mm Hg

Increasing ISS

Kutcher et al.17 115 20% MCL  Q  10% by ROTEM 52% Hypothermia (e36.0-C)Acidosis (pH  e  7.2)

INR  Q  1.3

aPTT  Q  30

Platelet count  G  200,000

Schochl et al.8 33 N/A Maximal lysis of 100% by ROTEM 88% ISS 9  25

aPTT, activated partial thromboplastin time; INR, international normalized ratio; MCL, maximal clot lysis N/A, not applicable.

 J Trauma Acute Care Surg Volume 74, Number 6    Napolitano et al.

*   2013 Lippincott Williams & Wilkins   1577

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cause of death (6.0% for the TXA group vs. 6.2% for the placebo group; RR, 0.97; 95% CI, 0.87 Y 1.08; p  = 0.60).

Evaluation of all-cause 28-day mortality by subgroupsconfirmed that the signal for benefit of TXA was in the most severe shock group as defined by admission SBP. In the sub-group of trauma patients presenting with SBP of 75 mm Hg

or less, all-cause 28-day mortality was 30.6% (478 of 1,562)for the TXA group versus 35.1% (562 of 1,599) for the placebogroup (RR, 0.87; 99% CI 0.76 Y 0.99).

Data Limitations in CRASH-2 TrialRed blood cell (RBC) transfusion was administered 

to approximately 50% of patients enrolled in the CRASH-2Trial (50.4% for the TXA group vs. 51.3% for the placebogroup), with mean (SD) units transfused 6.06 (9.98) for theTXA group versus 6.29 (10.31) for the placebo group. Nostandardized RBC transfusion protocol was used in the trial.Most of the study sites were in low- and middle-incomecountries where MT protocols and hemostatic resuscitation

are not routinely available. No data are available from this trial regarding additional

 blood products (plasma, platelets) administered, number and outcome of patients requiring MT, whether MT protocols wereused, or specific information regarding coagulopathy and in- jury severity. Furthermore, time to cessation of hemorrhageand information regarding thrombotic events were not cap-tured in this trial. These are significant limitations of theCRASH-2 Trial (Table 2).

TXA Added to World Health Organization Listof Essential Medicines

Based on the results of the CRASH-2 Trial, TXA wasrecently added to the World Health Organization list of es-sential medicines in March 2011:

&   ‘‘Section 10: addition of TXA injection for the treatment of adult patients with trauma and significant risk of on-going haemorrhage. On the basis of the results of a verylarge trial of the use of TXA specifically for trauma patients V including those who have been in road trafficaccidents, the Committee concluded that there is sufficient evidence to support the proposal that listing TXA maycontribute to a reduction in this cause of death.’’43,44

Cochrane Systematic Reviews V Antifibrinolytics

Antifibrinolytics for Acute Traumatic InjuryThe Cochrane systematic review regarding antifibri-

nolytic drugs for acute traumatic injury45 included all ran-

domized controlled trials (4 trials, n = 20,548 patients) of antifibrinolytic agents (aprotinin and TXA) following acutetraumatic injury. Two of these trials studied TXA in 20,451 patients, and one of the trials was the CRASH-2 Trial. TXAreduced the risk of death by 10% (RR, 0.90; 95% CI, 0.85 Y 0.97;

 p  = 0.0035). No additional information concerning vascular occlusive events beyond the data from CRASH-2 was pro-vided. The two aprotinin trials provided no reliable dataaccording to the authors of the Cochrane systematic review.

TABLE 2.   Significant Limitations of the CRASH-2 Trial

Study Limitation Comment

Approach to randomization: ‘‘Doctor is reasonably certain that antifibrinolytic agents are indicated or contraindicated  V donot randomize’’

Concern regarding selection bias

 No data regarding injury severity of the patient cohort (ISS, RTS) Unable to determine if cohorts are similar 

 No data regarding shock in the patient cohort (lactate, base deficit) Unable to determine if cohorts are similar 

Small sample size of hypotensive patients (SBP  e  90 mm Hg),which is target population

SBP  G  90 mm Hg in only 31.5% of study patients

Small sample size of tachycardic patients (HR  9  107), which istarget population

HR  9  107 in only 48% of patients

 No data regarding fibrinolysis on admission, no coagulation testing Rate of fibrinolysis at admission in North American trauma centers is  e5%

Only 1,063 deaths (35%) were caused by bleeding The most common cause of death was traumatic brain injury

TXA did not reduce blood transfusions Only 50% of study cohort received blood transfusion; Median (IQR) units of 

 blood product transfused 3 (2 Y 6) in total cohort. In transfused cohort, mean (SD)6.06 (9.98) for the TXA group vs. 6.29 (10.31) for the placebo group.

 No adverse events regarded as serious, unexpected, or suspected to berelated to the study treatment 

Concern about possible inadequate reporting

Patient follow-up reported as 100% Difficult to believe

Effect size small. Statistically significant but not clinically meaningfulfinding?

Study determined a 0.8% absolute reduction in ‘‘death caused by bleeding’’in 20,000 patients.

Absolute increase in mortality if TXA given 3 h after injury TXA treatment given after 3 h after injury was associated with an increased risk of deathcaused by bleeding (4.4% vs. 3.1%; RR, 1.44; 95% CI, 1.12  Y 1.84; p  = 0.004).

The aim of the CRASH-2 trial was to assess the effects of early administration of TXA on death, vascular occlusive events, and blood transfusion in trauma patients with significant 

hemorrhage.

Inclusion criteria include trauma patients judged to be 16 years or older, with significant hemorrhage (SBPG 90 mm Hg and/or heart rate9 110 beats per minute),or considered to be at 

risk of significant hemorrhage, within 8 hours of injury.

HR, heart rate; IQR, interquartile range; RTS, Revised Trauma Score.

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Antifibrinolytics for Minimizing PerioperativeRBC Transfusion

The Cochrane systematic review regarding antifibri-nolytic (TXA, aprotinin and epsilon aminocaproic acid [EACA]) use for minimizing perioperative allogeneic blood transfusion in adult surgical patients supports its use. This

review included 252 randomized controlled trials with morethan 25,000 participants and concluded that antifibrinolyticdrugs provide worthwhile reductions in blood loss and receipt of RBC transfusion and seem to be free of serious adverseeffects.46

TXA reduced the risk of blood transfusion by 39% (RR,0.61; 95% CI, 0.53 Y 0.70), but it did not reduce the need for reoperationdue to bleeding(RR, 0.80; 95% CI,0.55 Y 1.17) and mortality (RR, 0.60; 95% CI, 0.33 Y 1.10). Aprotinin reduced the need for reoperation due to bleeding by 54% (RR, 0.46;95% CI, 0.81 Y 0.99), and a similar trend was seen with EACA(RR, 0.32; 95% CI, 0.11 Y 0.99). Aprotinin (vs. TXA and EACA)was associated with a significant increase in the risk of death(RR, 1.39) and myocardial infarction (RR, 1.11). Sixty-five of 

the trials (n = 4,842) specifically comparedTXAwith a controlarm. An evaluation of these trials reveals that there was noincreased incidence of DVT, PE, myocardial infarction or stroke in the patients who received TXA.

However, this review did not include trials assessingthe effect of TXA in emergency surgery. A systematic reviewof randomized trials in adults undergoing emergency or urgent surgery identified 5 trials with 372 patients. TXA reduced the probability of receiving a blood transfusion by 30% (RR, 0.70;95% CI, 0.52 Y 0.94), but there was no impact on mortality (RR,1.01; 95% CI, 0.14 Y 0.73).47

Effect of TXA on Surgical Bleeding

The Cochrane systematic review on the effect of TXAon surgical bleeding included 129 trials (n = 10,488), withstudies performed between 1972 and 2011. TXA reduced the probability of receiving a blood transfusion by a third (RR,0.62; 95% CI, 0.58 Y 0.65;   p   G   0.001). This effect remained when the analysis was restricted to trials using adequate al-location concealment (RR, 0.68; 95% CI, 0.62 Y 0.74;   p   G

0.001). The effect of TXA on myocardial infarction (RR, 0.68;95% CI, 0.43 Y 1.09;   p   = 0.11), stroke (RR, 1.14; 95% CI,0.65 Y 2.00;   p   = 0.65), DVT (RR, 0.86; 95% CI, 0.53  Y 1.39;

 p = 0.54), and PE (RR, 0.61; 95% CI, 0.25 Y 1.47; p = 0.27) wasuncertain. Fewer deaths occurred in the TXA group (RR, 0.61;

95% CI, 0.38 Y 0.98; p = 0.04), although, when the analysis wasrestricted to trials using adequate concealment there was con-siderable uncertainty (RR, 0.67; 95% CI, 0.33 Y 1.34; p  = 0.25).The evidence is strong that TXA reduces blood transfusionin surgery, but the effect on thromboembolic events and mortality remains uncertain.48

Exploratory Analysis of CRASH-2: Early VersusLate TXA

The effect of TXA treatment on death caused by bleeding,rather than all-cause 28-day mortality, was examined. Thissubgroup analysis examined four baseline characteristics asfollows:(1) time from injury to treatment (e1, 91 Y 3,and 93h);(2) severity of hemorrhage as assessed by SBP (e75, 76 Y 89,and   989 mm Hg); (3) Glasgow Coma Scale (GCS) score(severe, 3 Y 8; moderate, 9 Y 12; mild, 13 Y 15); and (4) type of injury (penetrating only, blunt only, and blunt plus penetrating).These were the same subgroup analyses that were reported  previously but for the outcome of death caused by bleeding

rather than for all-cause mortality.49

Of the 3,076 deaths from all causes, 1,063 deaths (35%)were caused by bleeding. The risk of death caused by bleedingwas significantly reduced with TXA(4.9%vs. 5.7%; RR, 0.85;95% CI, 0.76 Y 0.96;   p  = 0.0077). There was no significant effect of TXA on the risk of death for all other (nonbleeding)causes combined (Table 3). Subgroup analysis confirmed asignificant reduction (19%) in deaths caused by bleeding(14.9% vs. 18.4%; RR, 0.81; 95% CI, 0.69  Y 0.95) in the most severe hemorrhagic shock patients with SBP of 75 mm Hg or less (Table 4).

Early TXA treatment (e1 hour from injury) was asso-ciated with the greatest reduction (32% reduction) in deaths

caused bybleeding (198 [5.3%]of 3,747for theTXA group vs.286 [7.7%] of 3,704 for the placebo group; RR, 0.68; 95%CI, 0.57 Y 0.82; p  G  0.0001). Treatment given between 1 hoursand 3 hours after injury also reduced the risk of death caused  by bleeding (147 [4.8%] of 3,037 vs. 184 [6.1%] of 2,996; RR,0.79; 95% CI, 0.64 Y 0.97;  p  = 0.03) (Tables 3 and 4).

In contrast, TXA treatment given after 3 hours after in- jury was associated with an increased risk of death caused by bleeding (144 [4.4%] of 3,272 vs. 103 [3.1%] of 3,362;RR, 1.44;95% CI, 1.12 Y 1.84; p  = 0.004). In patients given TXA 3 hoursafter injury, no effect of TXA on death caused by bleeding wasidentified in the SBP, GCS, or type of injury groups. The authors

TABLE 3.   RR (95% CI) of Death With TXA, Overall and by Time to Treatment in CRASH-2 Trial

n All Causes of Death Bleeding Death Nonbleeding Death

Overall 20,127 0.91 (0.85 Y 0.97), p  = 0.0035 0.85 (0.76 Y 0.96), p  = 0.0077 0.94 (0.86 Y 1.02), p  = 0.13

Time to treatment, h

e1 7,451 0.87 (0.76 Y 0.97) 0.68 (0.57 Y 0.82) 1.04 (0.89 Y 1.21)

913 6,033 0.87 (0.77 Y 0.97) 0.79 (0.64 Y 0.97) 0.91 (0.78 Y 1.05)

93 6,634 1.00 (0.90 Y 1.13) 1.44 (1.12 Y 1.84) 0.89 (0.78 Y 1.02)

W2 test of homogeneity   V    4.411 ( p = 0.11) 23.516 ( p  = 0.0000) 2.537 ( p = 0.28)

Primary outcome was 28-day all-cause mortality with cause of death described with the following categories: bleeding, vascular occlusion (myocardial infarction, stroke, and PE),

multiorgan failure, head injury, and other.

Adapted from CRASH-2 collaborators.49

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concluded that TXA should be given as early as possible to bleeding trauma patients. For trauma patients admitted lateafter injury, TXA treatment was harmful.

CRASH-2 Intracranial Bleeding Study (IBS)

CRASH-2 IBS was a prospective randomized controlled trial nested within the CRASH-2 Trial50 in patients (n = 270)who fulfilled the inclusion criteria for the CRASH-2 Trialand also had TBI (defined as GCS  e 14 and brain computed tomographic [CT] scan compatible with TBI). The primaryoutcome was increase of intracranial hemorrhage size betweena CT scanat hospital admission and a second CT scan 24hoursto 48 hours later.

TXA was associated with a nonsignificant reduction inhemorrhage growth (adjusted difference,   j3.8 mL, 95%credibility interval [CrI],  j11.5 mL to 3.9 mL), fewer focalischemic lesions (adjusted odds ratio [OR], 0.54, 95% CrI,0.20 Y 1.46) and fewer deaths (adjusted OR, 0.49, 95% CrI,

0.22 Y 

1.06) (Table 5). In the CRASH-2 IBS study, the majority(85%) of the observed deaths were caused by TBI, not bleeding.Inadequate sample size (n = 270) prohibits definitive con-clusions from this study.51

MATTERs Study The Military Application of TXA in Trauma Emergency

Resuscitation (MATTERs) study is a retrospective observa-tional study comparing TXA to no TXA in combat casualty patients (n = 896; 293 TXA) treated in a Role 3 surgical hospital

in southern Afghanistan. Trauma patients were identified fromUK and US trauma registries.52

The TXA group had lower unadjusted mortality thanthe no-TXA group (17.4% vs. 23.9%, respectively;  p  = 0.03)despite being more severely injured (mean [SD] ISS, 25.2[16.6] vs. 22.5 [18.5];  p   G  0.001). This benefit was greatest in MT patients (14.4% vs. 28.1%, respectively;   p   = 0.004),where TXA was also independently associated with survival(OR, 7.228; 95% CI, 3.016 Y 17.322) and less coagulopathy( p = 0.003).

Thrombotic events were significantly increased in theTXA group for both PE (8 [2.7%] vs. 2 [0.3%], p = 0.001 in theoverall cohort; 4[3.2%] vs. 0, p  = 0.001 in the MT cohort) and 

DVT (7 [2.4%] vs. 1 [0.2%],  p  = 0.001 in the overall cohort;2 [1.6%] vs. 1 [0.5%],   p   = 0.32 in the MT cohort). After correcting for severity of injury, there was no association of TXA use with an increased risk of DVT or PE.

TABLE 4.   Mortality Caused by Bleeding, by Subgroup Analysis in CRASH-2 Trial

TXA Placebo RR (95% CI)

Time to treatment, h

e1 198/3,747 (5.3%) 286/3,704 (7.7%) 0.68 (0.57 Y 0.82)

91 Y 3 147/3,037 (4.8%) 184/2,996 (6.1%) 0.79 (0.64 Y 0.97)

93 144/3,272 (4.4%) 103/3,362 (3.1%) 1.44 (1.12 Y 1.84)

W2 = 23.516,  p  G  0.0000

SBP, mm Hg

989 146/6,878 (2.1%) 163/6,761 (2.4%) 0.88 (0.71 Y 1.10)

76 Y 89 110/1,609 (6.8%) 114/1,689 (6.7%) 1.01 (0.79 Y 1.30)

e75 233/1,562 (14.9%) 295/1,599 (18.4%) 0.81 (0.69 Y 0.95)

W2 = 2.235,  p  = 0.33

GCS score

Severe (3 Y 8) 168/1,789 (9.4%) 186/1,830 (10.2%) 0.92 (0.76 Y 1.13)

Moderate (9 Y 12) 93/1,349 (6.9%) 121/1,344 (9.0%) 0.77 (0.59 Y 0.99)

Mild (13 Y 15) 228/6,915 (3.3%) 265/6,877 (3.8%) 0.86 (0.72 Y 1.02)

W2 = 1.275,  p  = 0.53

Type of injury

Blunt 308/6,788 (4.5%) 347/6,817 (5.1%) 0.89 (0.77 Y 1.04)Penetrating 181/3,272 (5.5%) 227/3,250 (7.0%) 0.79 (0.66 Y 0.96)

W2 = 0.923,  p  = 0.34

All deaths 489/10,060 (4.9%) 574/10,067 (5.7%) 0.85 (0.76 Y 0.96)

Two-sided  p  = 0.0077

Adapted from CRASH-2 collaborators.49

TABLE 5.   Effect of TXA on Outcomes in the CRASH-IBS

Unadjusted OR (95% CrI) n = 270 Adjusted OR (95% CrI) n = 270) Probability of Benefit, %

Mortality 0.57 (0.28 Y 1.14) 0.49 (0.22 Y 1.06) 96

Mortality caused by head injury 0.59 (0.28 Y 1.25) 0.54 (0.24 Y 1.22) 93

 Need for neurosurgery 0.98 (0.50 Y 1.93) 0.98 (0.50 Y 1.91) 53

Reprinted with permission from the Queens Printer and Controller of HMSO 2012.  Health Technology Assessment  2012; Vol. 16: No. 13. ISSN 1366  Y 5278.50

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The authors concluded that treatment with TXA should  be implemented into clinical practice as part of a resuscitationstrategy following severe wartime injury and hemorrhage. Thisstudy is limited, however, because of its retrospective observa-tional nature, lack of standardized indications and dosingof TXA, and no data regarding timing of TXA treatment or 

laboratory evaluation for fibrinolysis.53

MATTERs II Study The MATTERs II study expanded the sample size of 

the MATTERs I study to further evaluate TXA and traumaoutcomes. A review of 1,332 patients (identified from pro-spectively collected UK and US trauma registries) who re-quired one or more RBC unit transfusion were analyzed toexamine the impact of cryoprecipitate (CRYO) in addition toTXA on survival in combat injured patients.

Despite greater ISSs and RBC transfusion requirements,mortality was lowest in patients who received TXA (18.2%) or TXA/CRYO (11.6%) compared with CRYO alone (21.4%) or 

no-TXA/CRYO (23.6%). Logistic regression analysis con-firmed that TXA and CRYO were independently associated with a similarly reduced mortality (OR, 0.61; 95% CI, 0.42 Y 0.89;

 p = 0.01and OR, 0.61; 95% CI, 0.40 Y 0.94; p = 0.02, respectively).The combined TXA and CRYO effect versus neither in a synergymodel had an OR of 0.34 (95% CI 0.20  Y 0.58;   p   G   0.001),reflecting nonsignificant interaction ( p = 0.21).54

Military Damage-Control Resuscitation ClinicalPractice Guideline

The Joint Theater Trauma System Clinical PracticeGuideline for Damage-Control Resuscitation at forward surgicalhospitals and combat support hospitals includes evidence-based recommendations for TXA administration in combat casualtycare:55 ‘‘The early use of TXA (i.e.,  as soon as possible after injury but ideally not later than 3 hours post injury) should bestrongly considered for any patient requiring blood productsin the treatment of combat-related hemorrhage and is most strongly advocated in patients judged likely to require MT(e.g., significant injury and risk factors of MT).’’

Potential Thrombotic Complicationsof Antifibrinolytics

When evaluating the therapeutic benefits of hemostaticdrugs, we must also consider the risk of adverse events.56 Thefrequency of thrombotic events among trauma patients whoreceive antifibrinolytic agents is not fully known from the

clinical studies performed to date.The MATTERs study documented no difference in

thromboembolic events, but the retrospective nature of thisstudy limits any conclusions regarding thrombotic compli-cations related to TXA. The CRASH-2 Trial documented no difference in thromboembolic events (PE, DVT, stroke,myocardial infarction), but the event rates were very low, and no standard mechanism for diagnosis of these complicationswas mandated in the trial.

A systematic review of 57 studies of adults givenantifibrinolytic drugs for spontaneous bleeding (n = 5,049,3,616 [72%] had spontaneous subarachnoid hemorrhage)confirmed that the frequencies of limb ischemia and myocardial

infarction were less than 1% for TXA and EACA. The frequencyof DVT or PE was 1.9% for TXA versus 3.0% for EACA. Anotable finding, however, was a cerebral infarction rate of 9.7%for TXA versus 7.7% for EACA in studies of subarachnoid hemorrhage. This study concluded that thrombotic events haveoccurred infrequently with antifibrinolytic drugs after sponta-

neous bleeding, apart from subarachnoid hemorrhage, so further exploration of their safety and efficacy after spontaneous bleeding is justified in randomized trials.57

TXA in Trauma: How Did It Reduce Mortality?The CRASH-2 Trial documented no statistical differ-

ence in RBC transfusion between groups, so it is unclear whether the reduced mortality in the TXA group was caused  by the prevention of clot lysis and improved coagulation withdecreased bleeding after injury. TXA,as an antifibrinolytic agent,inhibits plasmin, which is known to induce proinflammatoryeffects by activation of monocytes, neutrophils, platelets, and endothelial cells and complement releasing lipid mediators

and cytokines and by induction of proinflammatory genes.

58,59

Some have speculated that improved survival in TXA patientsmay be caused by an attenuated inflammatory response achieved in part through reduction of circulating plasmin levels.60 Y 63 It remains unclear whether the mortality benefit from TXA isfrom reversal of fibrinolysis or whether an inflammatory or immune modulation is the underlying mechanism.

Cost-Effectiveness Analysis of CRASH-2 TrialThe incremental cost per life years gained for TXA use

in trauma was $48, $66, and $64 in Tanzania, India, and theUnited Kingdom, suggesting cost efficacy in low-, middle-,and high-income settings.64 TXA cost ($5.70 per gram) wastaken from the British National Formulary and converted into

international dollars, but there is significant US variability.

Additional TXA Clinical Trials in Traumaand Hemorrhage

CRASH-3 Trial: TXA for TBICRASH-3 is an international, multicenter, pragmatic,

randomized, double-blind, placebo-controlled trial to quantifythe effects of the early TXA versus placebo on death and disability in adult TBI patients (n = 10,000)65 who are within8 hours of injury and have intracranial bleeding on CT scanor GCS score 12 or less if the responsible doctor is substan-tially uncertain as to whether to use TXA.66,67

World Maternal Antifibrinolytic (WOMAN) Trial:TXA for Postpartum Hemorrhage

This is an international, randomized, double-blind, placebo-controlled trial investigating TXA for the treatment of post- partum hemorrhage.68,69 Obstetric hemorrhage is the leadingcause of maternal mortality, accounting for up to one third of deaths, most in the postpartum period. As of January 2013,5,657 women have been randomized (trial start, May 2009).

CRASH-2 Goes ViralDespite the compelling findings of the CRASH-2 trial

announced in 2010, an audit of UK hospitals in 2011 showed that, of 412 trauma patients who required blood transfusion

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and were eligible for TXA treatment, only 12 (3%) received TXA. On November 19, 2011, the CRASH-2 research teamrolled out an online brief video to assist in making cliniciansaware of this lifesaving treatment.70

Despite this novel approach of disseminating researchinformation from the CRASH-2 Trial, implementation of a

TXA protocol for trauma has still not been initiated in most trauma centers in the United States. A recent survey of 24member institutions of the Trauma Center Association of America documented that only 2 (one Level 1 and one Level 2trauma center) were using TXA as part of an institutional protocol and 7 institutions were considering its use. Reasonsreported for lack of TXA use included lack of availability,ineffectiveness, cost, and unfamiliarity with the drug.71

Analysis of TXA on Death/Thrombotic EventsAccording to Baseline Risk of Death

A recent analysis examined the effect of TXA in trauma patients stratified by risk of death at baseline.72 The baseline

risk of death was calculated using a prognostic model that was derived from the CRASH-2 Trial.73 The study cohort included 13,273 trauma patients in the CRASH-2 Trial whowere treated with TXA or placebo within 3 hours of injuryand trauma patients enrolled in the UK Trauma and Audit Research Network. TXA was associated with a significant reduction in all-cause mortality and deaths from bleeding ineach stratum of baseline risk. Interestingly, TXA was associ-ated with a significant reduction in the odds of fatal and nonfatal thrombotic events (OR, 0.69; 95% CI, 0.53  Y 0.89;

 p  = 0.005) and a significant reduction in arterial thromboticevents (OR, 0.58; 0.40 Y 0.83;   p  = 0.003) but no significant reduction in venous thrombotic events (OR, 0.83; 95% CI,0.59 Y 1.17; p  = 0.295) (Fig. 1).

Why the Delay in Implementing TXA in Trauma?The significant delay in implementation of TXA ad-

ministration in trauma is likely related to questions regardingwhich patients should receive it. Important knowledge gapsare present in the research to date, and additional researchefforts are warranted about the TXA use in trauma.74 We be-lieve that a prospective randomized study performed in acontrolled environment with laboratory monitoring of coag-ulation and standardized transfusion protocols is essential beforeTXA becomes standard of care in trauma. Based on the evi-dence to date, how should we implement TXA use in trauma?

One potential implementation strategy would be to

use the inclusioncriteria from the CRASH-2 Trial: use TXA inall patients with significant hemorrhage (SBP   G  90 mm Hgand/or heart rate  9  110 beats per minute) or considered to beat risk of significant hemorrhage within 8 hours of injury. Thiswould result in a large number of patients being treated withTXA who would not be expected to have fibrinolysis, includingthose patients more than 3 hours from injury in which the post hoc analysis documented a significantly increased risk of deathcaused by bleeding with TXA, so we do not recommend thisapproach.

Another implementation strategy is to initiate TXA use inthetrauma patient cohort most likely to derive benefitin mortalityreduction, that is, those with significant injury and more severe

hemorrhagic shock as identified by SBP 75 mm Hg or less and less than 3 hours from time of injury. This strategy will allowtrauma centers to review their TXA use data and outcomes on asmaller cohort of patients in an initial implementation protocolfor TXA use in trauma. A predictive model for mortality is being developed based on the CRASH-2 Trial data, and in the

future, this may assist clinicians in the determination of whichtrauma patients would most benefit from TXA treatment.Another approach is to use TXA only in patients with docu-mented HF by TEG or in those with risk factors for HF.

Summary: What Do We Know?&   TXA is associated with a 1.5% reduction in 28-day all-cause

mortality in adult trauma patients with signs of bleeding(SBP   G   90 mm Hg, heart rate   9  110 beats per minute, or  both, within 8 hours of injury) in a large pragmatic pro-spective randomized placebo-controlled trial.

&   What is critical is the modest effect on the overall popula-tion: All-cause mortality was ‘‘significantly’’ reduced from16.0% to 14I5% (NNT, 67). The risk of death caused by

 bleeding overall was ‘‘significantly’’ reduced from 5.7% to4I9% (NNT, 121).

&   TXA signal for benefit was in the most severe shock group(admission SBP  e  75 mm Hg), 28-day all-cause mortalityof 30.6% for the TXA group versus 35.1% for the placebogroup (RR, 0.87; 99% CI 0.76 Y 0.99).

&   1,063 deaths (35%) were caused by bleeding in theCRASH-2 Trial.

&   TXA had greatest impact on reduction of death caused by bleeding in the severe shock group (SBP   e   75 mm Hg)(14.9% vs. 18.4%; RR, 0.81; 95% CI, 0.69  Y 0.95).

&   Early TXA (e1 hour from injury) was associated with thegreatest reduction (32% reduction) in deaths caused by

 bleeding (5.3% vs. 7.7%; RR, 0.68; 95% CI, 0.57 Y 

0.82; p  G  0.0001).&   TXA given between 1 hour and 3 hours after injury also

reduced the risk of death caused by bleeding (4.8% vs.6.1%; RR, 0.79; 95% CI, 0.64 Y 0.97; p  = 0.03).

&   TXA given after 3 hours after injury was associated withan increased risk of death caused by bleeding (4.4% vs.3.1%; RR, 1.44; 95% CI, 1.12 Y 1.84; p  = 0.004).

&   TXA had no impact on TBI outcomes, but the study waslimited by small sample size.

&   TXA treatment is not associated with an increased risk of vascular occlusive events.

What Is Still Unknown?&   Whether TXA has any impact on trauma outcomes when

damage-control resuscitation or MT protocols are used;&   The mechanism by which TXA reduced mortality in trauma

in the CRASH-2 Trial. Fibrinolysis assessment and coag-ulation testing were not part of the study design, and de-termination of time to cessation of hemorrhage was not required in the study;

&   Whether fibrinolysis testing should be performed beforeconsideration of TXA treatment;

&   What is the optimal dose and timing of TXA in trauma;&   Whether other antifibrinolytic agents could be substituted 

for TXA use in trauma;

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&   Whether TXA is associated with higher seizure rates intrauma or TBI patients. Increased postoperative seizureshave been reported in cardiac surgery with TXA doses that are 2-fold to 10-fold higher than those used in CRASH-2.75 Y 80 These seizures have been associated with an in-creased incidence of neurologic complications (delirium

and stroke), prolonged recovery, and higher mortality rates.A proposed mechanism for seizures is TXA-mediated in-hibition of glycine receptors as a potential cause of neuro-toxicity.81,82 A recent warning has been added to the FDA

drug label: ‘‘Convulsions have been reported in associationwith tranexamic acid treatment.’’83

A Rational Approach for TXA use in Trauma&   In adult trauma patients with severe hemorrhagic shock 

(SBP  e  75 mm Hg), with known predictors of fibrinolysis,

or with known fibrinolysis by TEG (LY30  9 3%);&   Only administer TXA if less than 3 hours from time of injury;&   TXA administration: 1 g intravenously administered over 

10 minutes, then 1 g intravenously administered over 8 hours.

Figure 1.   Prespecified analysis of TXA effect on mortality and thrombotic events based on risk of death at baseline in trauma patients.A, Deaths from all causes in patients with traumatic bleeding according to treatment with TXA (p  = 0.96 for heterogeneity). B , Death

 from bleeding in patients with traumatic bleeding according to treatment with TXA (p = 0.98 for heterogeneity). C, Fatal and nonfatalthrombotic events in patients with traumatic bleeding according to treatment with TXA (p  = 0.74 for heterogeneity) (reproducedwith permission from BMJ Publishing Group Ltd. from Roberts et al.72).

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AUTHORSHIP

 All authors have made substantial contributions to this review, includingacquisition, analysis, and interpretation of data; drafting of the manu-script, and critical revision of the content. All authors take full respon-sibility for the data as presented.

DISCLOSURE

B.A.C. received funding from Haemonetics Corp. (Braintree, MA) for a multicenter investigator-initiated study evaluating the use of RapidTEG in severely injured patients. E.E.M. received research support from both Haemonetics Corp. (Braintree , MA) and Tem International(Munich, Germany) for TEG and ROTEM studies in trauma.

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